Engine/valvetrain with shaft-mounted cam followers having dual independent lash adjusters

Abstract

A multiple cylinder internal combustion engine having a valvetrain with a camshaft disposed within an engine block and at least two valves operated by a common camshaft lobe includes a stationary shaft disposed generally parallel to the camshaft and a cam follower having a first end with an opening pivotally mounted on the stationary shaft, a second end adapted for coupling to at least two pushrods each associated with one of the at least two valves, and a roller mounted on a roller axle disposed generally between the first and second ends, the roller contacting the common camshaft lobe. The cam follower may include independently operable lash adjusters for pushrods driven by a common camshaft lobe.

1. A multiple cylinder internal combustion engine having a valvetrain with a camshaft disposed within an engine block, the engine including at least two intake valves or at least two exhaust valves operated by a common camshaft lobe, the engine comprising:
 a stationary shaft disposed generally parallel to the camshaft 
 a cam follower having a first end with an opening concentrically and pivotally mounted on the stationary shaft, a second end adapted for coupling to at least two pushrods, each pushrod associated with one of the at least two intake valves or exhaust valves, and a roller mounted on a roller axle disposed generally between the first and second ends, the roller contacting the common camshaft lobe; 
 a rocker arm associated with each pushrod for actuating one of the at least two intake valves or at least two exhaust valves; and the cam follower comprises: 
 at least two independent lash adjusters, each lash adjuster associated with a corresponding pushrod and rocker arm. 
 
   
   
     2. The engine of  claim 1  wherein the at least two independent lash adjusters comprise:
 at least two independent hydraulic lash adjustment mechanisms. 
 
   
   
     3. The engine of  claim 1  wherein the stationary shaft is disposed within the engine block and includes a channel for supplying pressurized oil to the hydraulic lash adjustment mechanisms. 
   
   
     4. A multiple cylinder internal combustion engine having a valvetrain with a camshaft disposed within an engine block, the engine including at least two intake valves or at least two exhaust valves operated by a common camshaft lobe, the engine comprising:
 a stationary shaft disposed generally parallel to the camshaft 
 a cam follower having a first end with an opening concentrically and pivotally mounted on the stationary shaft, a second end adapted for coupling to at least two pushrods, each pushrod associated with one of the at least two intake valves or exhaust valves, and a roller mounted on a roller axle disposed generally between the first and second ends, the roller contacting the common camshaft lobe; 
 a rocker arm associated with each pushrod for actuating one of the at least two intake valves or at least two exhaust valves; 
 wherein the cam follower comprises: 
 a housing; 
 a first sleeve disposed within a first bore in the housing and having a closed end and an open end; 
 a first plunger disposed within the first sleeve and defining a first high-pressure chamber between the closed end and the first plunger; 
 a first check valve disposed between the first plunger and the first sleeve for controlling flow of hydraulic fluid from the first plunger into the first high-pressure chamber, the hydraulic fluid in the high-pressure chamber along with the plunger spring operating to remove lash associated with a first push rod, first rocker arm, and first valve; 
 a second sleeve disposed within a second bore in the housing and having a closed end and an open end; 
 a second plunger disposed within the second sleeve and defining a second high-pressure chamber between the closed end and the second plunger; and 
 a second check valve disposed between the second plunger and the second sleeve for controlling flow of hydraulic fluid from the second plunger into the second high-pressure chamber, the hydraulic fluid in the second high-pressure chamber along with the plunger spring operating to remove lash associated with a second push rod, second rocker arm, and second valve. 
 
   
   
     5. The engine of  claim 4  wherein each of the first and second plungers comprises:
 a lower plunger member contacting a corresponding check valve; and 
 an upper plunger member disposed between the lower plunger member and an associated pushrod, the upper plunger member adapted for coupling with the associated pushrod and having an orifice for supplying hydraulic fluid to the associated pushrod. 
 
   
   
     6. The engine of  claim 5  wherein the upper plunger member includes an orifice in a generally convex hemispherical end for coupling to the associated pushrod. 
   
   
     7. A valvetrain for a multiple cylinder internal combustion engine having a camshaft disposed within an engine block for operating two intake valves or two exhaust valves from a single camshaft lobe, the valvetrain comprising:
 a cam follower having a first end with an opening concentrically mounted for pivoting about a stationary shaft extending generally parallel to the camshaft in the engine block, the cam follower having a second end with first and second hydraulic lash adjusters positioned above a roller for contacting the camshaft lobe; 
 first and second rocker arms each associated with a respective one of the two valves; and 
 first and second pushrods extending between the first and second lash adjusters of the cam follower and first and second rocker arms, respectively. 
 
   
   
     8. The valvetrain of  claim 7  wherein the two valves are intake valves associated with the same cylinder. 
   
   
     9. The valvetrain of  claim 7  wherein the first and second lash adjusters comprise hydraulic lash adjusters having a high-pressure chamber containing a variable amount of hydraulic fluid to remove lash from a respective pushrod, rocker arm, and valve assembly. 
   
   
     10. A cam follower for an internal combustion engine having a pushrod valvetrain including a camshaft and a stationary shaft disposed within an engine block, the stationary shaft extending generally parallel to the camshaft, the cam follower comprising:
 a housing having a first end with an opening for pivotal mounting to the stationary shaft and a second end having first and second hydraulic lash adjusters at least partially disposed within the housing, each having one end adapted for coupling with a corresponding pushrod, the lash adjusters including a variable volume chamber fillable with hydraulic fluid supplied through the housing from the stationary shaft to adjust axial distance of a corresponding pushrod relative to the housing; and 
 a roller for contacting a camshaft lobe, the roller being mounted for rotation about an axle mounted in the housing. 
 
   
   
     11. The cam follower of  claim 10  wherein the first and second lash adjusters include a generally hemispherical end for coupling with a corresponding generally hemispherical end of a pushrod. 
   
   
     12. The cam follower of  claim 11  wherein the generally hemispherical end is convex. 
   
   
     13. The cam follower of  claim 10  wherein the first and second hydraulic lash adjusters comprise:
 a sleeve disposed within a corresponding bore in the housing and having a closed end and an open end; 
 a plunger disposed within the sleeve and axially movable relative thereto defining a variable volume high-pressure chamber between the closed end and the plunger; and 
 a check valve disposed between the plunger and the sleeve for controlling flow of hydraulic fluid from the plunger into the high-pressure chamber. 
 
   
   
     14. A method for actuating at least two intake valves or at least two exhaust valves associated with a single cylinder in a multiple cylinder internal combustion engine having a camshaft disposed within an engine block, the method comprising:
 opening the at least two gas exchange valves substantially simultaneously using at least two corresponding pushrods and rocker arms coupled to a common cam follower mounted for pivoting about a stationary cylindraceous shaft extending generally parallel to the camshaft; 
 wherein the common cam follower independently adjusts lash associated with each pushrod and rocker arm. 
 
   
   
     15. The method of  claim 14  wherein the internal combustion engine includes four valves per cylinder and wherein the step of actuating comprises actuating two intake valves. 
   
   
     16. The method of  claim 14  further comprising positioning the stationary shaft within an engine block above the camshaft. 
   
   
     17. A method for actuating at least two intake valves or at least two exhaust valves associated with a single cylinder in a multiple cylinder internal combustion engine having a camshaft disposed within an engine block, the method comprising:
 opening the at least two gas exchange valves substantially simultaneously using at least two corresponding pushrods and rocker arms coupled to a common cam follower mounted for pivoting about a stationary cylindraceous shaft extending generally parallel to the camshaft; and 
 automatically adjusting for lash in the at least two corresponding pushrods and rocker arms by supplying pressurized hydraulic fluid to independent lash adjusters of the common cam follower. 
 
   
   
     18. The method of  claim 17  wherein the step of supplying comprises supplying pressurized hydraulic fluid to the common cam follower through the stationary shaft.